Wireless control of tightly spaced machines

ABSTRACT

Embodiments herein describe wireless transmission techniques for mitigating interference between wirelessly controlled machines in a shared space. To mitigate interference, the machines may be assigned different channels within the same frequency band. However, if machines using the same channel in a frequency band receive each other&#39;s wireless signals, the wireless signals can interfere. To free up additional bandwidth, in one embodiment, the command signals are transmitted using a different frequency band than a heartbeat signal used to stop the machines in case of emergencies. In another embodiment, time multiplexing or directional antennas can be used to mitigate interference. In another example, antenna diversity and multiple-input-multiple output (MIMO) can be used to further focus the radiation pattern onto the desired machine while avoiding transmitting wireless signals to neighboring machines. In one embodiment, the machines may use dual-channels to transmit and receive duplicate data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/795,017, filed on Oct. 26, 2017. The aforementioned relatedpatent application is herein incorporated by reference in its entirety.

BACKGROUND

Automation relies on machines to perform tasks such as transportingitems between locations in a warehouse, assembling or manufacturingproducts, sorting items, packaging items, removing items from packaging,and the like. The machines may be controlled using wireless signals froma controller. Bandwidth becomes limited as more and more machines whichrely on wireless control are spaced closer together. For example, toreduce the amount of occupied floor space (e.g., the footprint), amanufacturer or distributor may space the wirelessly controlled machinessuch that the wireless signals transmitted for controlling one machinecan interfere with the wireless signals transmitted to another,neighboring machine.

To mitigate interference, the wireless signals transmitted to onemachine may use a different wavelength (or range of wavelengths) thanthe wireless signals transmitted to another machine. In this manner, themachines can be allocated different portions of the bandwidth usingnon-interfering wireless signals. However, as the density of machinesincreases, the amount of bandwidth (e.g., the available wavelengths)becomes limited. Because of bandwidth constraints, the same wavelengthsmay be used to transmit controls to two different machines. If thesignals transmitted to one of the machines reach the other machine, thesignals can cause interference which prevents that machine from reliablereceiving the wireless signals intended for it.

BRIEF DESCRIPTION OF DRAWINGS

Various embodiments in accordance with the present disclosure will bedescribed with reference to the drawings, where like designations denotelike elements.

FIG. 1 illustrates an item-sortation machine, according to variousembodiments.

FIG. 2 is a flowchart for controlling robots in a machine using aheartbeat signal and wireless instructions, according to variousembodiments.

FIG. 3 illustrates using multiple wireless frequency bands and multiplechannels to mitigate interference between tightly spaced machines,according to various embodiments.

FIGS. 4A and 4B illustrate using time multiplexing to mitigateinterference between tightly spaced machines, according to variousembodiments.

FIG. 5 illustrates changing assigned channels between neighboringmachines, according to various embodiments.

FIG. 6 illustrates using multiple antennas to mitigate interferencebetween tightly spaced machines, according to various embodiments.

FIG. 7 illustrates assigning multiple repeaters with limited range tomitigate interference between tightly spaced machines, according tovarious embodiments.

FIGS. 8 and 9 illustrate transmitting duplicate data on multiplechannels to tightly spaced machines, according to various embodiments.

FIG. 10 is a flowchart for transmitting command and heartbeat signals ondifferent frequency bands, according to various embodiments.

FIG. 11 is a flowchart for transmitting duplicate data using twochannels in the same frequency band, according to various embodiments.

FIGS. 12 and 13 illustrate an apparatus for sorting items, according tovarious embodiments.

DETAILED DESCRIPTION

Embodiments herein describe wireless transmission techniques formitigating interference between wirelessly controlled machines in ashared space—e.g., a warehouse or plant. As the density of the machinesincreases, the demand for bandwidth may also increase. For example, manywireless communication standards—e.g., IEEE 802.11a/b/g/n/ac/ad—providedifferent channels for allocating bandwidth within their definedfrequency band (e.g., 2.4 GHz, 5 GHz, or 60 GHz). That is, the differentchannels may correspond to a different wavelength or range ofwavelengths in the frequency band. For example, each channel in the 2.4GHz frequency band is 20 MHz wide. Machines that use different channelsin the frequency band can generally communicate without interfering witheach other (although some portions of the channels may be overlapping).However, wireless signals in the 2.4 GHz and 5 GHz frequency bands cantravel up to 100 feet. Moreover, different machines may require multiplechannels to operate. If the channels have to be re-used (e.g., differentmachines use the same channels to communicate) and the machines are notspread far enough apart, then the wireless signals can interfere witheach other and prevent the corresponding machines from reliablyreceiving the signals. However, spreading out the machines to preventinterference means that more floor space (e.g., a bigger footprint) isrequired to operate the machines which may increase costs. The wirelesstechniques described herein permit the machine density to be increasedwhile mitigating the likelihood the wireless signals intended for onemachine interfere with another machine.

Many machines use a heartbeat signal (e.g., a continuous signal) as anemergency stop (E-stop) signal to stop the machines in case of anemergency. The heartbeat signal also requires bandwidth in the frequencyband (although the bandwidth may be smaller than the bandwidth use totransmit operational commands to the machines). In one embodiment, theheartbeat signal is assigned to a first frequency band while theoperational commands are assigned to a second frequency band. Forexample, the heartbeat signal may be assigned to the 2.4 GHz band whilethe operational commands are transmitted on the 5 GHz band (or viceversa). To mitigate interference between neighboring machines, themachines may be assigned different channels within the same frequencyband. For example, Machine A is assigned Channel 1, Machine B isassigned Channel 2, and so forth. However, there are a limited number ofchannels in each frequency band and some machines may require multiplechannels further restricting the bandwidth. Thus, the channels may haveto be reused which can result in interference if the machines are withinwireless range of each other. For example, wireless signals for IEEE802.11a/b/g/n/ac have a range up to approximately 100 feet. If machinesusing the same channel in one of these IEEE frequency bands are within100 feet of each other, the wireless signals can interfere.

In one embodiment, time multiplexing is used to mitigate interference.The machines can all use the same channel (or channels) but at differenttimes. For example, Machine A may use the channel during a first timeslot, Machine B uses the channel during a second time slot, Machine Cduring a third time slot, and so forth. Because only one machine isusing the channel at a time, the signals cannot interfere. However, thisreduces the amount of data that can be transmitted to the machines sincethey receive/transmit signal only during their time slot. However,multiple channels in the 2.4 of 5 GHz bands could be used to send datawhich can increase the bandwidth, or the machines may use a higherbandwidth frequency band such as IEEE 802.11ad which has a 60 GHzfrequency band.

In one embodiment, a directional antenna can be used to mitigateinterference between machines. The directional antenna can be positionedto focus the wireless signals (i.e., the antenna's radiation pattern)into an area that includes only one machine which may mitigate theamount of wireless signals that propagate in a direction away from themachine. As such, the machines can be spaced closer or permit themachines to use the same channels to transmit data with little or nointerference. In another example, antenna diversity andmultiple-input-multiple output (MIMO) can be used to further focus theradiation pattern onto the desired machine while not transmittingwireless signals to neighboring machines.

In one embodiment, the machines may use dual-channels to transmit andreceive data. That is, a controller may transmit the same data using twochannels in the same frequency band to the machine. Even if aneighboring machine is using the same channels at the same time, thelikelihood the wireless signals for a neighboring machine will interferewith both channels is low. To further decrease the risk of interference,antenna diversity and MIMO can be used to reduce the likelihood thewireless signals propagate between neighboring machines.

FIG. 1 illustrates an item-sortation machine 100, according to variousembodiments. Generally, the machine 100 sorts received items 125 intocontainers 180 using wirelessly controlled robots 140. However, thewireless communication techniques described herein are not limited tosuch and can be used in any wireless controlled machine (or robot(s))such as a machine for moving containers or racks in a warehouse,removing an item from a package, packing an item into a shippingcontainer, picking an item, and the like. The embodiments herein can beused in any machine that relies on wireless control signals which caninterfere with other wireless controlled machines in a shared area(e.g., a warehouse, sorting facility, mail processing facility, packingfacility, etc.).

The sortation machine 100 includes a master control system 105, a feeder130, a robot area 135, and a distribution system 170. The master controlsystem 105 provides the wireless control signals using a mastercontroller 110 and antenna 120 (e.g., a transmit antenna) which controlthe actions of the robots 140 in the robot area 135. For example, themaster control system 105 may wirelessly send move commands, pick-upcommands, drop commands, stop commands, and the like which control howthe robots 140 move themselves, and the item 125, in the robot area 135.The master control system 105 also includes a heartbeat controller 115which uses the antennas 120 to transmit a wireless heartbeat (or E-stop)signal to the robots 140. In one embodiment, the robots 140 perform thecommands received from the master controller 110 only as long as theheartbeat signal is received. That is, if the heartbeat controller 115stops sending the heartbeat signal, the robots immediately stop (e.g.,within a few millisecond) their current task. In one embodiment, theheartbeat signal is used to stop the robots 140 in the case of anemergency or a malfunction. Because the robots 140 could hurt a humannear the machine 100 or damage the machine 100 during a malfunction,once an emergency is detected, the heartbeat controller 115 candeactivate the heartbeat signal which immediately stops the robots 140to prevent harm to a human operator or the machine 100 itself. Theheartbeat controller 115 may deactivate the heartbeat signal in responseto a human operator pressing an emergency button, detecting amalfunctioning robot 140, sensor information (e.g., a vibration sensor),and the like. Once the emergency is handled, the heartbeat controller115 can resume transmitting the heartbeat signal which indicates to therobots 140 they can begin to perform the commands received from themaster controller 110.

In one embodiment, the master controller 110 and the heartbeatcontroller 115 include processors or micro-controllers. The mastercontroller 110 and the heartbeat controller 115 can include solelyhardware and firmware or can include combinations of hardware andsoftware elements. Although not shown, the control system 105 caninclude master controllers 110 for multiple different machines 100. Forexample, the control system 105 can refer to multiple independentlyoperating master controllers 110 for controlling respective machines100, synchronized master controllers 110, or a single master controller110 which controls multiple different machines 100.

The feeder 130 is a structure that moves the item 125 into the robotarea 135. For example, the robot area 135 may be an enclosure thatestablishes an area where the robots 140 move. The feeder 130 may be achute which slides the item 125 into a receiving area in the robot area135, a conveyor belt which moves the packages into the area 135, or acontainer in which a human places the items 125. In any case, the robots140 can retrieve the item 125 once the item 125 arrives in the robotarea 135 and use the commands received from the master control system105 to move the item to the distribution system 170 where the item isstored in one of the containers 180.

The machine 100 can include any number of robots 140, e.g., one, two,three, four, etc. As shown, each robot 140 includes a transport device145, a movement system 150, a power source 155, a controller 160, and atleast one antenna 165. The transport device 145 permits the robot 140 tocarry the item 125 to different locations in the robot area 135. Forexample, the robot area 135 may be a fenced off enclosure on thewarehouse floor or a frame which includes tracks which the robots 140can follow. The robots 140 can move along the floor and/or verticallyusing the frame. In another example, a portion of the robots 140 (or theentire robot) may remain stationary in the robot area 135. For instance,the base of the robot 140 may be anchored while an extension of therobot (e.g., a robotic arm) can move to pick up the items 125 and movethem to different locations. The transport device 145 may include a clawor suction cup for lifting or picking the item 125. In another example,the transport device 145 may be a conveyor that receives the item 125from a conveyor belt in the feeder 130. In another embodiment, thetransport device 145 may be a bin in which the feeder 130 places theitem 125.

The movement system 150 may move the entire robot 140 or a portion ofthe robot 140 within the robot area 135. For example, the movementsystem 150 may include wheels or bearings which permit the robot 140 tomove along the floor or along tracks. In another example, the movementsystem 150 includes an arm attached to the transport device 145 to movethe item 125. For example, the robot area 135 may include a centralconveyor belt that moves received items 125 past the robots 140. Themaster controller 110 can instruct a selected one of the robots 140 topick up the item 125 as it passes using the movement system 150 and thetransport device 145 to place the item 125 into the distribution system170.

The power source 155 in the robots 140 can be a battery or a capacitor.For example, the robots 140 may move relative short distances (e.g.,less than 50 feet) before they return to recharge. In that case, thecharge on a large capacitor (or capacitors) can be sufficient to movethe robot 140 before the robot 140 returns to a charging station or railto recharge the capacitor. The advantage of using a capacitor as thepower source 155 is that it can provide high currents and recharge in ashorter time than a battery, although either is acceptable. In anotherexample, if the entire robot 140 does not move within the robot area135, then the robot can be connected to a power grid (e.g., plugged intoa power outlet) where the power source 155 can be a power converter.

The controller 160 can be a processor or a micro-controller whichreceives commands from the master controller 110 using the antenna 165and issues corresponding commands to the transport device 145 andmovement system 150. For example, if the master controller 110 instructsthe robot 140 to move the item 125 to a particular location in the robotarea 135, the controller 160 in turn issues one or more commands to themovement system 150 to move the robot to the desired location. In oneembodiment, in addition to receiving information from the mastercontroller 110, the controller 160 can transmit information to themaster controller 110. For example, the controller 160 may use theantenna 165 to inform the master controller 110 when a command has beencompleted successfully. The controller 160 may send other informationwirelessly to the master controller 110 such as the charge on the powersource 155, status of the transport device 145 or movement system 150(if there is a malfunction or needs repair), if the item 125 wasdropped, and the like. In one embodiment, the controller 110 may beentirely hardware, but in other embodiments may include a combination ofhardware/firmware and software.

In one embodiment, the distribution system 170 receives the item 125from the robot 140 and places the item 125 in one of the containers 180.The distribution system 170 may be multiple access apertures (e.g., afiling system) with corresponding chutes that lead to the containers180. Using the transport devices 145, the robots 140 can move the items125 through the apertures in the distribution system 170 and into thecontainers 180. In another example, the distribution system 170 mayinclude fasteners or platforms for coupling the containers 180 to thedistribution system 170. For instance, distribution system may form arack on which the containers 180 are mounted. The robots 140 can travelto the portion of the rack that stores the corresponding container 180for the package and place the item 125 into the container 180.

In one embodiment, the containers 180 are assigned differentdestinations either within the warehouse or to an external location(e.g., a different warehouse or mailing code). Moreover, the containers180 may correspond to different shipping companies. In one embodiment,the master controller 110 knows the desired destination of the items125, which may be determined by scanning a bar code or reading an RFIDtag on the item 125 when in the feeder 130. The master controller 110can then provide instructions to the robots 140 to move the item 125 tothe appropriate location in distribution system 170 such that the item125 is stowed in the container 180 corresponding to its destination. Inthis manner, the item-sortation machine 100 can provide wirelesscommands to the robots 140 for sorting received items 125 into thecontainers 180.

FIG. 2 is a flowchart of a method 200 for controlling robots in amachine using a heartbeat signal and wireless commands, according tovarious embodiments. For ease of explanation, the method 200 describescontrolling the robots 140 in the item-sortation machine 100 shown inFIG. 1. However, the method 200 can be used to control any kind ofwireless controlled machine such as a single robot or a cluster ofrobots.

At block 205, the master controller determines instructions for a robotto move an item to a desired location. For example, the mastercontroller may instruct the robot to pick up an item, move the item (oritself) to a different location, drop of the item, transfer the item toanother robot, and the like. As used herein, the wireless command caninclude any command sent from the master controller to the robot tocontrol the actions of the robot.

At block 210, the master controller wirelessly transmits the instructionto the robot. The master controller may transmit the instruction to atransmitter in the control system which uses on or more antennas totransmit commands to receivers in the robots. The transmitter in thecontrol system can use various wireless transmission algorithms such asantenna diversity and MIMO to mitigate interference between neighboringmachines.

At block 215, the heartbeat controller determines whether an E-stop hasbeen triggered. For example, the machine (or the surrounding area) mayinclude emergency stop buttons that can be pressed by a human operatorin case of an emergency or malfunction. For example, if the operatorneeds to retrieve a dropped package or notices a malfunctioning robot,the operation can press the emergency button which triggers the E-stop.In another embodiment, the heartbeat controller triggers the E-stopwithout human input. The heartbeat controller may monitor sensors in themachine or receive periodic or emergency status updates for the robots.Using this information, the heartbeat controller can determine totrigger the E-stop.

If the E-stop is triggered, the method 200 proceeds to block 220 wherethe heartbeat controller ceases transmitting the heartbeat signal. Inone embodiment, the heartbeat signal is a continuous signal with apredictable pattern such as a sine wave, a square wave, or a periodicpulse. In one example, the robots 140 may not receive commands using theheartbeat signal but rather monitor the signal to make sure they cancontinue to operate. Stated differently, the heartbeat signal may nottransmit digital data to the robots but instead provides a deactivationsignal for stopping the robots. As such, when the heartbeat controllerstops transmitting the heartbeat signal at block 220, the controller inthe robot may immediately stop the robot from moving (if currentlymoving) and prevent the robot from carrying out any commands that may bereceived from the master controller. In one embodiment, the controllerin the robot may put the robots in a passive state so that the robotscan be easily moved by the operator (in case the robot has malfunctionedor needs to be moved to address a safety concern or to retrieve a fallenitem).

To improve safety, it may be desired that robots stop immediately whenthe heartbeat signal stops (e.g., less than a second and preferably lessthan a few milliseconds). As such, the embodiments herein describetechniques for mitigate interference that may occur from wirelesssignals transmitted by neighboring machines in a shared area. Forexample, separate heartbeat signals may be transmitted to neighboringmachines. If those heartbeat signals reach both machines, then they caninterfere with each other such that the robots may incorrectly determinethat the heartbeat signal has ceased and stop its current action.Alternatively, if the E-stop is triggered for one of the machines, therobots in that machine may still receive the heartbeat signal intendedfor a neighboring machine and continue to operate which can lead to anunsafe situation.

If at block 225 the heartbeat controller determines the problem whichtriggered the E-stop is resolved, the method proceeds to block 230 wherethe heartbeat controller resumes transmitting the heartbeat signal andthe master controller can resume normal control and operation of therobots in the machine. However, if the problem has not been resolved,the absence of the heartbeat signal keeps the machine in a shutdownstate.

Returning to block 215, if the E-stop has not been triggered, the robotperforms the command so long as the heartbeat signal is received. Thatis, in addition to checking that the heartbeat signal is active when anew command is received at the robot, the controller in the robot maycontinue to perform the action or actions indicated in the command onlyas long as the heartbeat signal remains active. For example, thecontroller may have a separate detection system which continuallymonitors the heartbeat signal to detect when the signal stops. Inresponse, the detection system transmits an interrupt or override signalwhich stops the other functions in the controller. So long as theheartbeat signal remains active, the method 200 can repeat with therobots in the machine receiving new instructions or commands from themaster controller and performing those commands.

FIG. 3 illustrates using multiple wireless frequency bands and multiplechannels to mitigate interference between tightly spaced machines,according to various embodiments. Specifically, FIG. 3 illustrates a topview of a shared space 300 (e.g., floor space in a warehouse,fabrication plant, assembly plant, sort center, etc.) that includes aplurality of machines 100 which are spaced a distance (d) apart. Each ofthe machines 100A-D corresponds to an antenna 120A-D used by respectivemaster controllers (not shown) for transmitting commands to the machines100. The machines 100 may include one or more robots (not shown) whichthen receive the commands to perform corresponding actions.

Each of the antennas 120 have a corresponding radiation pattern 305which graphically represent the distance the wireless signals travelwithin the shared space 300. For the 2.4 GHz frequency band which isdefined by IEEE 802.11b/g/n standards and the 5 GHz frequency band whichis defined by IEEE 802.11a/h/j/n/ac standards, the signals may propagateup to 100 feet. Thus, given the circular radiation pattern shown in FIG.3 (as viewed from the top), the wireless signals transmitted by theantennas 120 may reach neighboring machines that are within 100 feet.Here, the distance (d) is less than 100 feet such that the radiationpatterns 305 overlap at least one, if not two or more of the neighboringmachines 100.

To prevent or mitigate interference between the machines, in thisembodiment, the heartbeat signals are assigned to a different frequencyband than the command signals. For example, the heartbeat signal may betransmitted on the 2.4 GHz frequency band while the command signals usedto control the machines 100 are transmitted on the 5 GHz frequency band(or vice versa). In this manner, interference between the heartbeatsignal and the command signals are mitigated. However, as shown by theradiation pattern 305A, the heartbeat or commands signals transmitted bythe antenna 120A can reach the machine 100B which means the wirelesssignals for controlling the machine 100A can cause interference at themachine 100B. To mitigate this intra-band interference, the wirelesssignals can be assigned to different channels within the frequency band.For example, the command signals transmitted to machine 100A use Channel1 in Frequency Band 1, the command signals transmitted to machine 100Buse Channel 2 in Frequency Band 1, the command signals transmitted tomachine 100C use Channel 3 in Frequency Band 1, and so forth. Similarly,the heartbeat signals transmitted to machine 100A can use Channel 1 inFrequency Band 2, the heartbeat signals transmitted to machine 100B useChannel 2 in Frequency Band 2, the heartbeat signals transmitted tomachine 100C use Channel 3 in Frequency Band 2, and so forth. In thismanner the command signals are allocated different portions of thebandwidth in Frequency Band 1 while the heartbeat signals are allocateddifferent portions of the bandwidth in Frequency Band 2. The antennas120 assigned to transmit the command and heartbeat signals for themachines 100A-D can transmit these signals in parallel with little or nointerference despite the overlapping radiation patterns 305.

In one embodiment, the heartbeat signal is assigned to use the frequencyband that has the least amount of bandwidth between the two frequencybands (e.g., the fewest number of channels). That is, because theheartbeat signal may not transmit data but rather a continuous signal,it may have more flexible bandwidth requirements than the commandsignals, and use less bandwidth. Moreover, instead of assigning aseparate channel for each machine 100 for the heartbeat signal, multiplemachines 100 may use the same heartbeat signal. For example, if thereare not enough channels in the frequency band for each machine 100 tohave its own channel for transmitting the heartbeat signal, multiplemachines may use the same channel to receive the heartbeat. Thus, if anyone of the machines in the group trigger an E-stop, all of the machines100 in the group stop. Stopping all the machines in the group may beacceptable so that a machine does not continue to operate even though anE-stop was triggered because a neighboring machine 100 within wirelessrange uses the same channel to transmit its heartbeat signal. Bygrouping the machines to use the same heartbeat signal so that thechannels are not reused by different heartbeat controllers, the operatorcan ensure that a machine (which triggered an E-stop) does notinadvertently receive a heartbeat signal on the same channel intendedfor a different machine.

If the distances (d) between the machines 100 shrinks and additionalmachines 100 are added to the shared space, there may not be enoughpre-defined channels in the frequency bands to assign unique channels toeach of the machines as shown in FIG. 3. Alternatively, the bandwidth ofa single channel may not be sufficient to provide data to the robots ineach of the machines 100. For example, using a single channel may besufficient to transmit the command signals if each of the machines 100has less than five robots, but if the machines 100 have more than fiverobots than at least two channels are used, and if the machines 100 havemore than ten robots, at least three channels are used. As such,multiple channels may be assigned to each of the machines 100 totransmit the command signals. In either case, the frequency bands maynot have a sufficient number of channels to assign all the machines 100within the radiation patterns 305 of each of the machines 100 a uniquechannel (or channels). For example, if a frequency band has only twentychannels but there are twenty other machines 100 within the radiationpattern 305A of the antenna 120A for the machine 100A, then the humanoperator may have to use the same channel assigned to the machine 100Ato one of the other machines within the radiation pattern 305A which cancause interference. Thus, the embodiments described in FIG. 3 can becombined with other embodiments described below (or other embodimentsmay be used instead of what is shown in FIG. 3) to mitigate interferencewhen the machine density increases or when there is no more availablebandwidth (e.g., all the channels in the frequency bands have beenused).

FIGS. 4A and 4B illustrate using time multiplexing to mitigateinterference between tightly spaced machines, according to variousembodiments. FIG. 4A illustrates the shared space 300 that includes themachines 100 but uses time multiplexing to mitigate interference. Forexample, the embodiments in FIG. 4A may be used if the machine densityor bandwidth requirements in the shared space 300 does not permit usingthe wireless strategy shown in FIG. 3. In FIGS. 4A and 4B, each of themachines 100 is assigned a respective timeslot or time slice to performwireless communication during which time the antennas 120 for the otherneighboring machines 100 are not transmitting wireless signals.

In FIG. 4A, the antenna 120A transmits wireless signals while theantennas 120 for the other wireless machines (i.e., machines 100B-D) areunused. For example, the antenna 120A may transmit command signals onChannel 1 of Frequency Band 1 without having to worry about interferencefrom the neighboring machines 100. Moreover, although FIG. 4Aillustrates assigning only one channel, in other embodiments multiplechannels can be used by the machines 100 during their respectivetimeslots. For example, each of the machines 100 may use Channels 1-10during their timeslot to transmit command signals. Thus, even though themachines cannot transmit command signals continuously, they can usemultiple channels to transmit more commands than could be transmitted ifonly one channel is used. For example, when not transmitting, the mastercontrollers for the machines 100 may queue the commands for the machineand then transmit the queued commands during the next timeslot.

In one embodiment, the heartbeat signal is time multiplexed in the samemanner as shown in FIGS. 4A and 4B; however, this means the machines 100can perform the commands only during their timeslot. Instead, theheartbeat controller may continuously transmit the heartbeat signal sothat the machines 100 can operate continuously. For example, even thoughin FIG. 4A only the antenna 120A is transmitting commands to the machine100, the other machines 100 can nonetheless be operating using commandsthat were received previously. For example, in a previously time slot,the master controller for the machine 100B may have instructed a robotto move four centimeters or to activate its conveyor belt to pick up anitem. Because it may take the robot several seconds to complete thiscommand, so long as the heartbeat signal is still being received, thecontroller in the robot can issue instructions to perform this commandeven if the robot is not currently wirelessly communicating with themaster controller. Because the heartbeat signal may require lessbandwidth than the command signals, there may be sufficient availablebandwidth to permit each machine 100 to have its own channel for theheartbeat signals (or share the same channel) so that the heartbeatsignals can be transmitted continuously.

In FIG. 4B, the antenna 120A has ceased transmitting the command signals(e.g., its timeslot has ended) and the antenna 120B begins transmittingduring the timeslot assigned to the machine 100B (i.e., Timeslot 2).Again, if the heartbeat signal is transmitted continuously for all themachines 100, the robots in the machine 100A can continue to operate toperform the commands received during Timeslot 1. In this manner, each ofthe machines can transmit command signal during respective timeslotusing the same channels without interference.

In one embodiment, multiple antennas may transmit command signalssimultaneously in the shared space 300. For example, each machine 100may not use all the channels to transmit data during its timeslot. Assuch, a neighboring machine may use the remaining channel to transmitdata during the same timeslot. For example, the machine 100A may useChannels 1-5 during Timeslot 1 to transmit command signals in parallelwith the machine 100D using Channels 6-10 to transmit command signals.Because the machines 100 use different channels, there is little or nointerference. Of course, if two machines are sufficient far away in theshared space 300 such that the signals transmitted by one machine cannotinterfere with the signals received by the other machine, then bothmachines can transmit command signals using the same channel orchannels. The operator may identify which machines 100 in the sharedspace 300 are sufficiently far away from a selected machine (e.g.,machine 100A or 100B) such that there is no interference, and thendetermine which machines can use the same timeslot to transmit wirelesssignals using the same channel as the selected machine.

In one embodiment, the master controllers for each of the machines 100are synchronized so that each controller knows when to transmit thecommand signals. For example, the master controllers for the machines100A-D may share the same clock signal or periodically transmitsynchronization signals to each other to ensure that two of the antennas120 are not transmitting on the same channel in parallel. For example,once the machine 100A determines its timeslot has expired, it can notifythe master controller for the machine 100B to begin its timeslot. Inanother embodiment, instead of having separate master controllers foreach machine 100, there is one master controller for all the machines100 which can manage the timeslots for the machines 100.

FIG. 5 illustrates changing assigned channels between neighboringmachines 100, according to various embodiments. As shown, FIG. 5illustrates a shared space 500 that includes the machines 100A-D thateach have a respective a directional antenna 510A-D. Instead ofomnidirectional antennas 120 as shown in FIGS. 3 and 4A-4B, thedirectional antennas 510 have directional radiation patterns 505. Inthis example, the radiation patterns 505 include at least one main lobewhich covers a respective machine 100. The main lobes taper as theyapproach neighboring machines 100 which reduces the likelihood that, forexample, the wireless command signals transmitted by the directionalantenna 510A interfere with the receivers in the machine 100B. That is,the directional antennas 510 may be configured or arranged in the sharedspace 500 such that neighboring machines are in nulls for the radiationpatterns 505 to reduce interference.

In FIG. 5, the directional antennas 510 transmit wireless commandsignals simultaneously to the machines 100. That is, in one embodiment,the machines 100 are not time multiplexed. A distance d2 between amachine (e.g., the machine 100A) and its direct neighbor (e.g., themachine 100B) may be short enough (e.g., less than 30 feet) such thatthe command signals transmitted by the antennas 510 can interfere. Assuch, the directly neighboring machines 100 are assigned differentchannels in the frequency band. That is, the antenna 510B uses Channel 2but the directly neighboring antennas 510A and 510C use Channel 1.Because the distance d1 may be large enough (e.g., more than 30 feet)such that the wireless signals transmitted by the antenna 510A do notinterfere with the machine 100C (or the machine 100D), the antenna 510Aand 510C can use the same channel. Thus, using the directional antennas510 with narrowed beam patterns 505 can mean the operator assigns twodifferent channels (or two different groupings of channel such asChannels 1-5 and 6-10) to directly neighboring machines.

Of course, if the distances d1 and d2 are shrunk further, the radiationpattern 505A may also overlap with the machine 100C which can causeinterference. As such, the machine 100C may be assigned to communicateusing Channel 3 to mitigate interference. Moreover, the machine 100Dcould use Channel 1 since it may be outside the radiation pattern 505Aused by the machine 100A. In another example, as the distance d2increases (or the directional antenna 510A has a sufficiently narrowradiation pattern 505A), all of the machines 100 can use the samechannel (or group of channels) so long as the radiation patterns 505 donot overlap with the directly neighboring machines 100.

In FIG. 5, the heartbeat signal 515 is assigned to a different frequencyband (e.g., Frequency Band 2) from the frequency band used by thecommand signals. If the heartbeat signal 515 is also transmitted using adirectional antenna, then the heartbeat signals 515 can be assignedusing a similar scheme as the command signals shown in FIG. 5. Forexample, given the distances d1 and d2 shown here, the heartbeat signal515 for the machine 100A may be transmitted on Channel 1 of theFrequency Band 2, the heartbeat signal 515 for the machine 100B isassigned Channel 2 of the Frequency Band 2, the heartbeat signal 515 forthe machine 100C is assigned Channel 1 of the Frequency Band 2, and soforth. As the distances d1 and d2 vary, so can the channel assignmentsfor the heartbeat signal 515. In another embodiment, the heartbeatsignal 515 is transmitted in the same frequency band (e.g., theFrequency Band 1) as the command signals. For example, the heartbeatsignal may be shared by all the machines 100A-D in FIG. 5 and useChannel 3 of the Frequency Band 1, in which case the heartbeat signalmay be transmitted using an omnidirectional antenna. Or, the radiationpattern 505 (or the distances between the machines 100) may permit themachines 100 to use the same channel of the same frequency band withoutinterference from a neighboring antenna transmitting its independentheartbeat signal 515.

FIG. 6 illustrates using multiple antennas to mitigate interferencebetween tightly spaced machines, according to various embodiments. Asshown, FIG. 6 illustrates a shared space 600 where multiple antennasarranged in antenna groups 610 transmit command signals to the machines100. That is, instead of using one antenna to transmit command signalsto the machines using one or more channels, each machine 100 hasmultiple antennas in an antenna group 610 to transmit the data signals.The antenna groups 610 can be assigned a single channel or multiplechannels in a frequency band.

In one embodiment, the antenna groups 610 use antenna diversity andMIMO. Doing so provides the master controllers for the machines 100 withmore control of the radiation patterns 605 corresponding to the antennagroups 610. In one embodiment, in addition to having multiple antennasfor transmitting the command signals, each robot in the machines 100includes multiple receive antennas for receiving the command signals.For example, MIMO uses multiple transmit and receive antennas to exploitmultipath propagation in the shared space 600. Using precoding (orbeamforming), the master controller uses the antenna group 610 to causeconstructive interference of the signals emitted by the antennas at aparticular location within the machines 100. That is, the mastercontroller can increase the received signal at a robot by making signalsemitted from the different antennas to add up constructively and toreduce the effect of multipath fading. Thus, MIMO permits the mastercontroller to further control the radiation pattern 605 to reduceinterference between the neighboring machines 100. In FIG. 6, theantenna groups 610 can all use the same channel (or plurality ofchannels) to transmit commands to the machines with little or nointerference.

Using MIMO and antenna diversity can permit the machines 100 to bespaced closer together than, for example, using the omnidirectionalantennas 120 shown in FIG. 3 or the directional antennas 510 in FIG. 5.For example, the machines 100 in FIG. 5 may have to spread out adistance of at least 30 feet to prevent interference if all the machines100 are assigned the same channel. By using antenna groups 610 and MIMO,the machines 100 in FIG. 6 may be spaced less than 30 feet apart andstill use the same channel (or same group of channels) to communicate.If the distance between the machines 100 is reduced further, then theoperator can assign the channel like what is shown in FIG. 5 wheredirectly neighboring machines 100 are assigned different channels.However, the distances between the machines 100 in FIG. 6 may be smallerthan the distances between the machines in FIG. 5 thereby increasing thedensity of the machines and enable a more efficient use of the sharedspace 600.

Further, the antennas in the antenna groups 610 may be directionalantennas. That is, the use of directional antennas can be combined withantenna diversity and MIMO in order to further reduce the radiationpatterns 605 and mitigate or prevent interference between the machines100.

The heartbeat signal 615 may be assigned to the same frequency band usedby the command signals (e.g., Frequency Band 1) or a different frequencyband (e.g., Frequency Band 2). If the heartbeat signal 615 is alsotransmitted using an antenna group implementing antenna diversity andMIMO, then the heartbeat signals 615 can be assigned using a similarscheme as the command signals shown in FIG. 6 where individuallycontrollable heartbeat signals 615 are transmitted without worryingabout interference. In other embodiments, the heartbeat signal 615 istransmitted using a single antenna (e.g., without MIMO) in which caseheartbeat signal 615 may be assigned different channels for the machines100 to mitigate interference, or the signal 615 may be shared bymultiple machines 100 in which case the heartbeat signal 615 may betransmitted using an omnidirectional antenna rather than a directionalantenna to increase its coverage area. As an example of the latter, themachines 100A-D may use the same heartbeats signal 615 which may reducedeployment cost, although this means if one of the machines 100experiences an E-stop and the heartbeat signal 615 is not transmitted,all the machines listening for the heartbeat signal 615 also stop.

FIG. 7 illustrates assigning multiple repeaters 710 (e.g., synchronizedantennas to transmit the same signals on the same channel in parallel)with limited range to mitigate interference between tightly spacedmachines 100, according to various embodiments. FIG. 7 illustrates ashared space 700 where each machine 100 includes multiple repeaters 710(three repeaters 710 per machine 100 in this example, but the machines100 could include any number) disposed at different locations along alength of the machines 100. In one embodiment, the repeaters 710 for thesame machine transmit the same data—e.g., command signals—on the samechannel or groups of channels. Because of the limited range of radiationpatterns 705 for the repeaters 710, the neighboring machines 100 can usethe same channel or group of channels to transmit the command signalssimultaneously in the same frequency band. That is, the repeaters 710A-Ctransmit command signals to the robots in the machine 100A at the sametime the repeaters 710D-F transmit command signals to the robots in themachine 100B on the same channel (Channel 1).

Instead of using directional antennas, antenna diversity, or MIMO, theradiation patterns 705 can be limited or controlled by the transmissionpower of the repeaters 710 or by using a frequency band with a limitedtransmission range (or a combination of both). For example, depending onthe distance between the machines 100, the operator can reduce thetransmission power of the repeaters 710 to ensure the radiation patterns705 do not overlap a neighboring machine 100. As the distance betweenthe machines 100 shrink, the operator may also reduce the transmissionpower to prevent interference. However, the operator may have to installadditional repeaters 710 to cover the layout of the machines 100. Forexample, after reducing the radiation patterns 705, there may be deadspots (e.g., portions of the machine 100 that are not within anyradiation pattern 705 of a repeater 710). As a result, the operator mayneed to space the repeaters 710 closer together along the length of themachines 100 and add another repeater 710 to remove the dead spot.

In another example, the repeaters 710 may operate in a frequency bandwith a smaller range than the 2.4 GHz and 5 GHz frequency bands. Forexample, the 60 GHz frequency band has a much smaller transmissiondistance than the 2.4 GHz and 5 GHz frequency bands. Thus, the repeaters710 may transmit command signals using the 60 GHz frequency band whichenables the machines 100 to be spaced closer together relative to usingslower frequency bands. Moreover, in addition to transmitting in afaster frequency band (which has a shorter transmission distance), theoperator can also reduce the transmission power of the repeaters 710 tofurther control the radiation patterns 705. In one embodiment, therepeaters 710 are directional antennas rather than omnidirectionalantennas as shown in FIG. 7 and are arranged such that theircorresponding radiation patterns extend primarily along the length ofthe assigned machine 100 rather than to a neighboring machine 100.

The heartbeat signal 715 may be assigned to the same frequency band usedby the command signals (e.g., Frequency Band 1) or a different frequencyband (e.g., Frequency Band 2). In one embodiment, each machine 100includes a second set of repeaters 710 for transmitting an individuallycontrollable heartbeat signal 715 for each machine which generateslittle or no interference with neighboring machines 100. In otherembodiments, the heartbeat signal 715 is transmitted using a singleantenna (e.g., without MIMO) in which case heartbeat signal 715 may beassigned different channels for the machines 100 to mitigateinterference, or the signal 615 may be transmitted on the same channeland shared by multiple machines 100.

FIG. 8 illustrates transmitting duplicate data on multiple channels totightly spaced machines 100, according to various embodiments. As shown,each machine 100 in the shared space 800 has two antennas 810 fortransmitting command signals to the robots within the machine 100. Forexample, the machine 100A includes the antennas 810A and 810B whichtransmit the same command signals to the robots in the machine 100A. Theremaining machines 100B-D also include a respective pair of antennas810. In this embodiment, the antenna 810A has a radiation pattern 805A(shown as the solid line) for transmitting the command signals while theantenna 810B has a radiation pattern 805B (shown as the dashed line).Although the antennas 810A and 810B transmit the command signals at thesame time, there is little or no interference between the signalsbecause the antenna 810A uses Channel 1 of the Frequency Band 1 whilethe antenna 810B uses Channel 2 of the Frequency Band 1. The antennapairs for the other machines 100B-D have a similar configuration.

Although the antenna pairs do not interfere with each other, thetransmitted signals can interfere with neighboring machines as shown bythe overlapping radiation patterns 805. That is, the command signalstransmitted by the antennas 810A and 810C on the machines 100A and 100Bmay interfere since both antennas use Channel 1 to communicate and haveradiation patterns 805 that extend to neighboring machines 100. Stateddifferently, the wireless signals emitted by the antenna 810A can bereceived by the robots in the machine 100B at the same time those robotsare receiving command signals transmitted by the antenna 810C. Theinterference from the antenna 810A can prevent the robots in the machine100B from receiving the commands emitted by the antenna 810C. However,because the master controller can send identical data (e.g., the samecommand signals) on both of the antennas 810C and 810D in the machine100B using two different channels, the controller can reduce thelikelihood that interference from a neighboring antennas prevent therobots from receiving the commands. In one embodiment, the distancebetween the machines 100 is controlled that it is unlikely thatinterference emitted by neighboring antennas prevent the robots fromreceiving the commands emitted by the pair of antennas for that machine100. For example, the IEEE 802.11ad standard permits a receiver toselect the best beam forming link from a two-channel receiver (with twoantennas) depending on which channel signal path link has betterperformance. Thus, if Channel 1 is currently receiving a lot ofinterference, the receiver on the robots can receive the command signalsusing Channel 2. In this manner, the operator can re-use channels inneighboring machines 100 thereby freeing up available bandwidth whilemitigating the likelihood that interference from neighboring antennasusing the same channels prevents the robots from receiving commandsignals from at least one of the antennas assigned to the machine 100.

The heartbeat signal 815 may be assigned to the same frequency band usedby the command signals (e.g., Frequency Band 1) or a different frequencyband (e.g., Frequency Band 2). In one embodiment, each machine 100includes a second set of antenna pairs for transmitting an individuallycontrollable heartbeat signal 815 for each machine which generateslittle or no interference with neighboring machines 100. For example,each machine 100 may include two antennas for transmitting the heartbeatsignal 815 on Frequency Band 2 using two different channels. Thereceivers in the robots can then select which of the channels providesthe best version of the heartbeat signal. Thus, when a neighboringmachine (which uses the same two channels to transmit its heartbeatsignal 815) introduces interference on one of the channels, thereceivers can receive the heartbeat signal using the other channel.While FIG. 8 illustrates using pairs of antennas to send out duplicatecommand or heartbeat signals, in other embodiments each machine may usethree, four, or more antennas for transmitting duplicate command signalsor the heartbeat signal 815 on additional channels (e.g., Channels 3, 4,5, etc.) to reduce the likelihood that interference can prevent therobots from receiving on all the channels.

FIG. 9 illustrates transmitting duplicate data on multiple channels totightly spaced machines, according to various embodiments. Like in FIG.8, each machine 100 in the shared space 900 has at least two antennasfor transmitting duplicate data (e.g., either command signals or theheartbeat signal 915) to the robots in the machines. However, unlike inFIG. 8 where only one antenna transmits in each channel, in FIG. 9,multiple antennas (e.g., antenna groups 910) are assigned to eachchannel. That is, the antenna group 910A uses Channel 1 to transmitcommand or heartbeat signals to the robots in the machine 100A while theantenna group 910B uses Channel 2 to transmit duplicate data to therobots in the machine 100A. These channels are then re-used by theneighboring machines. That is, the antenna groups 910C and 910D whichtransmit duplicate data to the robots in the machine 100B also useChannel 1 and 2, respectively. As mentioned above, the robots can havemultiple antennas for receiving the duplicate data and select whichsignal has the best channel signal path link.

Moreover, because each antenna group 910 includes multiple antennas, thegroups 910 can use antenna diversity and MIMO to reduce inter-machineinterference. As shown, the radiation patterns 905 corresponding to eachof the antenna groups 910 are not omnidirectional like the radiationpatterns 805 in FIG. 8. For example, the radiation pattern 905A shown bythe solid line (Which corresponds to the antenna group 910A) and theradiation pattern 905B shown by the dashed line (which corresponds tothe antenna group 910B) have main lopes that primarily cover the machine100A. The radiation patterns 905A and 905B may have nulls at thelocations of the other machines 100B-D in the shared space 900 therebyfurther mitigating the likelihood that the wireless signals emitted bythe antennas in the shared groups 910A and 910B interfere withneighboring machines 100. Thus, the pair of antenna groups 910 assignedto each machine 100 can use the channels that are also used by theantenna groups 910 in neighboring machines 100 as shown. In this manner,the available bandwidth is increased so that the machines 100 can betightly spaced even if the radiation patterns 905 may overlap with, orcause interference at, neighboring machines 100.

The heartbeat signal 915 may be assigned to the same frequency band usedby the command signals (e.g., Frequency Band 1) or a different frequencyband (e.g., Frequency Band 2). In one embodiment, each machine 100includes a second set or pair of antenna groups 910 for transmitting anindividually controllable heartbeat signal 915 for each machine whichgenerates little or no interference with neighboring machines 100. Forexample, each machine 100 may include four antennas arranged in two newantenna groups 910 for transmitting the heartbeat signal 915 onFrequency Band 2 using two different channels. The receivers in therobots can then select which of the channels provides the best versionof the heartbeat signal. Thus, when a neighboring machine (which usesthe same two channels to transmit its heartbeat signal 915) introducesinterference on one of the channels, the receivers can receive theheartbeat signal using the other channel. While FIG. 9 illustrates usingtwo antennas in each antenna group 910 to send out duplicate command orheartbeat signals, in other embodiments each machine may use three,four, or more antennas per group 910 for transmitting duplicate commandsignals or the heartbeat signal 915 to reduce the likelihood thatinterference can prevent the robots from receiving on all the channels.

Except as otherwise stated, the frequency bands discussed above can beinterchanged. For example, the frequency bands can be the 2.4 GHz, 5Ghz, 60 GHz, or other frequency bands. Moreover, the selection of thefrequency bands for the embodiments described above can depend on thedesired spacing or distance between the machines. For example, asdistance between the machines 100 is reduced or available bandwidth onthe 2.4 GHz or 5 GHz frequency bands is reduced, the command signals maybe transmitted using the 60 GHz frequency band while the heartbeatsignal is transmitted on a different frequency band.

FIG. 10 is a flowchart of a method 1000 for transmitting command andheartbeat signals on different frequency bands, according to variousembodiments. At block 1005, the master controller transmits wirelesscommands to a wireless controlled machine (which may include one or moreindividual controlled robots) using a first channel in a first frequencyband. At block 1010, the heartbeat controller transmits the heartbeatsignal using a second frequency band. In one embodiment, blocks 1005 and1010 occur in parallel. Further, the method 1000 may include controllingthe wireless command and heartbeat signals transmitted to neighboringwirelessly machines to mitigate interference as described in theembodiments above for FIGS. 3, 4A-4B, 5, 6, and 7.

At block 1015, the wirelessly controlled machine operates in response tothe received command so long as the heartbeat signal is received. Putdifferently, if the heartbeat control stops transmitting the heartbeatsignal, the wireless controlled machine stops performing the receivedcommands. Once the heartbeat signals resumes, the wireless controlledmachine can again resume performing the commands received from themaster controller.

FIG. 11 is a flowchart of a method 1100 for transmitting duplicate datausing two channels in the same frequency band, according to variousembodiments. At block 1105, the master controller transmits commands toa wirelessly controlled machine using a first channel in a frequencyband. At block 1110, the master controller transmits the same commandsto the wirelessly controlled machine using a second channel in thefrequency band. In one embodiment, blocks 1005 and 1010 occur inparallel. Further, the method 1100 may include controlling the wirelesscommand and heartbeat signals transmitted to neighboring wirelesslymachines to mitigate interference as described in the embodiments abovefor FIGS. 8, and 9.

At block 1115, the wirelessly controlled machine selects the commandsreceived on the channel with the best signal characteristic. Forexample, the machine may select the data from the channel that has themost gain or the best signal to noise ratio. In one embodiment, whenusing the 60 GHz frequency band, the technique for selecting which ofthe channels to use is described in IEEE 802.11ad for selecting the bestbeam forming link from a two-channel receiver depending on which channelsignal path link has better performance or signal characteristics.

Referring now to FIGS. 12 and 13, an apparatus which is one example ofan item sortation machine 100 shown in FIG. 1 for sorting items such asdocuments or mail pieces is designated generally 1200. The system 1200includes a plurality of delivery cars 1305 (e.g., the robots 140 shownin FIG. 1) to deliver items (e.g., item 125) to a plurality of sortlocations, such as output bins 1245 (e.g., containers 180). At a loadingstation 1255, each car 1305 receives an item from an input station 1205and delivers it to the appropriate bin.

The cars 1305 travel along a track 1230 to the sort locations. The trackhas a horizontal upper rail 1235 and a horizontal lower rail 1250, whichoperates as a return leg. A number of parallel vertical track legsextend between the upper rail 1235 and the lower return rail 1250. Inthe present instance, the bins 1245 are arranged in columns between thevertical track legs.

After a piece is loaded onto a car, the car travels upwardly along twopairs of vertical tracks legs and then horizontally along two uppertracks 1235. The car 1305 travels along the upper rail until it reachesthe appropriate column containing the bin for the piece that the car iscarrying. The track 1230 may include gates to direct the car 1305 downthe vertical legs where the car stops at the appropriate bin. The car1305 then discharges the piece into the bin using a transport device orsystem.

After discharging the piece, the car 1305 continues down the verticallegs of the column until it reaches the lower rail 1250 which the carfollows until returning to the loading station 1255 to receive anotheritem.

The cars 1305 are semi-autonomous vehicles that each have an onboardpower source (e.g., power source 155) and an onboard motor (e.g., amovement system 150) to drive the cars along the track 1230. The carsalso include a loading/unloading mechanism (e.g., the transport device145), such as a conveyor, for loading pieces onto the cars anddischarging the pieces from the cars.

Since the system 1200 includes a number of cars 1305, the positioning ofthe cars is controlled to ensure that the different cars do not crashinto each other. In one embodiment, the system 1200 uses a mastercontroller (e.g., the master controller 110 in control system 105) thattracks the position of each car 1305 and provides wireless commands toeach car to control the progress of the cars along the track. The mastercontroller may also control operation of the various elements along thetrack, such as the gates. Further, the control system may output aheartbeat signal, e.g., using a heartbeat controller 115. The cars 1305perform the commands to move the pieces throughout the apparatus 1200 solong as the heartbeat signal is active as described above.

At the input station 1205, the mail pieces are separated from oneanother so that the pieces can be conveyed serially to the loadingstation 1255 to be loaded onto the cars 1305. Additionally, at the inputstation information is determined for each piece using, for example, abar code scanner or a mailing address so that the piece can be sorted tothe appropriate bin.

A variety of configurations may be used for the input station, includingmanual or automatic configurations or a combination of manual andautomated features. In a manual system, the operator enters informationfor each piece and the system sorts the mail piece accordingly. In anautomatic system, the input system includes elements that scan each mailpiece and detect information regarding each piece. The system then sortsthe mail piece according to the scanned information.

In an exemplary manual configuration, the input system includes a workstation having a conveyor, an input device, and a monitor. The operatorreads information from a mail piece and then drops the piece onto aconveyor that conveys the piece to the loading station 1255.

In an exemplary automatic configuration, the system includes an imagingstation, having an imaging device such as a high speed line scanningcamera. In one example, the imaging station scans a bar code on eachmail piece to detect information regarding the destination for eachpiece. The system analyzes the image data to determine the destinationinformation and then controls the cars to move the piece into a bincorresponding to the destination.

FIGS. 12 and 13 illustrate such an automated system. A feeder 1210 inthe input bin serially feeds mail pieces from the input bin to aconveyor 1215. An imaging station 1220 positioned along the conveyorscans the mails pieces as the pieces are conveyed to the loading station1255. The system 1200 analyzes a bar code or mailing address to readinformation for the mail piece.

The conveyor 1215 conveys the mail piece to the loading station 1255where it is loaded onto a car 1305.

The input station 1205 may be configured in a wide range of options. Theoptions are not limited to those configurations described above, and mayinclude additional features, such as an automated scale for weighingeach piece, a labeler for selectively applying labels to the mail piecesand a printer for printing information on the mail pieces or on thelabels.

In one embodiment, the system 1200 includes a plurality of inputstations which may increase the feed rate of pieces. In addition, theinput stations may be configured to process different types of items. Inthis way, each input station could be configured to efficiently processa particular category of items. For instance, if the system isconfigured to process documents, such as mail, one input station may beconfigured to process standard envelopes, while another input stationmay be configured to process larger mails, such as flats. Similarly, oneinput station may be configured to automatically process mail byscanning it and automatically determining the recipient. The secondinput station may be configured to process rejects, such as by manuallykeying in information regarding the recipient.

The system includes a sorting station 1240 which includes an array ofbins 1245 for receiving the pieces. Additionally, the sorting station1240 includes the track 1230 for guiding the cars 1305 to the bins 1245.

In one embodiment, during transport, the cars travel up a pair ofvertical legs from the loading station 1255 to the upper rail 1235 (inone example, the cars actually travel up two pairs of rails because thetrack includes a forward track and a parallel opposing track). The carthen travels along the upper rail until reaching the column having theappropriate bin. The car then travels downwardly along two frontvertical posts and two parallel rear posts until reaching theappropriate bin, and then discharges the mail piece into the bin. Thecar then continues down the vertical legs until reaching the lowerhorizontal leg 1250. The car then follows the lower rail back toward theloading station.

As can be seen in FIG. 13, the track 1230 includes a front track 1310and a rear track 1315. The front and rear tracks 1310, 1315 are paralleltracks that cooperate to guide the cars around the track. In oneembodiment, each of the cars includes four wheels: two forward wheel andtwo rearward wheels. The forward wheels ride in the front track, whilethe rearward wheels ride in the rear track. It should be understood thatin the discussion of the track the front and rear tracks 1310, 1315 aresimilarly configured opposing tracks that support the forward andrearward wheels of the cars. Accordingly, a description of a portion ofeither the front or rear track also applies to the opposing front orrear track.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

In the preceding, reference is made to embodiments presented in thisdisclosure. However, the scope of the present disclosure is not limitedto specific described embodiments. Instead, any combination of thedescribed features and elements, whether related to differentembodiments or not, is contemplated to implement and practicecontemplated embodiments. Furthermore, although embodiments disclosedherein may achieve advantages over other possible solutions or over theprior art, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the scope of the present disclosure. Thus,the preceding aspects, features, embodiments and advantages are merelyillustrative and are not considered elements or limitations of theappended claims except where explicitly recited in a claim(s).

As will be appreciated by one skilled in the art, the embodimentsdisclosed herein may be embodied as a system, method or computer programproduct. Accordingly, aspects may take the form of an entirely hardwareembodiment, an entirely software embodiment (including firmware,resident software, micro-code, etc.) or an embodiment combining softwareand hardware aspects that may all generally be referred to herein as a“circuit,” “module” or “system.” Furthermore, aspects may take the formof a computer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be usedto implement embodiments of the invention. The computer readable mediummay be a computer readable signal medium or a computer readable storagemedium. A computer readable storage medium may be, for example, but notlimited to, an electronic, magnetic, optical, electromagnetic, infrared,or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium would include thefollowing: an electrical connection having one or more wires, a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), an optical fiber, a portable compact disc read-onlymemory (CD-ROM), an optical storage device, a magnetic storage device,or any suitable combination of the foregoing. In the context of thisdocument, a computer readable storage medium is any tangible medium thatcan contain, or store a program for use by or in connection with aninstruction execution system, apparatus or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Aspects of the present disclosure are described with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodimentspresented in this disclosure. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality and operation of possible implementations ofsystems, methods and computer program products according to variousembodiments. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment or portion of code, whichcomprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block may occurout of the order noted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A system, comprising: a first wirelesslycontrolled machine comprising at least one receive antenna; and acontrol system comprising at least one transmit antenna, wherein thecontrol system is configured to: wirelessly transmit first commands tothe first machine using a first frequency band, and wirelessly transmita first heartbeat signal to the first machine using a second frequencyband different from the first frequency band, wherein the first machineperforms the first commands so long as the first heartbeat signal isreceived.
 2. The system of claim 1, wherein the control system isconfigured to: transmit the first commands during a first timeslot andnot transmit the first commands during a second timeslot; and transmitthe first heartbeat signal during both the first and second timeslots.3. The system of claim 1, further comprising: a second wirelesslycontrolled machine disposed in a shared space with the first machine,wherein at least one of the first commands and the first heartbeatsignal reach a receive antenna in the second machine, wherein thecontrol system is configured to wirelessly transmit second commands tothe receive antenna of the second machine using a first channel in thefirst frequency band, wherein the first commands are transmitted to thefirst machine using a second channel in the first frequency band.
 4. Thesystem of claim 3, wherein the control system is configured towirelessly transmit a second heartbeat signal to the receive antenna ofthe second machine using a first channel in the second frequency band,wherein the first heartbeat signal are transmitted to the first machineusing a second channel in the second frequency band.
 5. The system ofclaim 1, further comprising: a plurality of transmit antennas comprisingthe at least one transmit antenna, wherein the control system isconfigured to, using the plurality of transmit antennas, transmit thefirst commands to the first machine using MIMO.
 6. The system of claim1, further comprising: a plurality of repeaters comprising the at leastone transmit antenna that is disposed at different locations along alength of the first machine, wherein the control system is configured totransmit the first commands to the first machine using the plurality ofrepeaters, wherein the plurality of repeaters use a same channel in thefirst frequency band to transmit the first commands.
 7. The system ofclaim 1, further comprising: a second wirelessly controlled machinedisposed in a shared space with the first machine; and a thirdwirelessly controlled machine disposed in the shared space, wherein thethird machine is spaced a greater distance from the first machine thanthe second machine in the shared space, wherein the control system isconfigured to wirelessly transmit the first commands to the firstmachine using a first channel in the first frequency band, wirelesslytransmit second commands to the second machine using a second channel inthe first frequency band, and wirelessly transmit third commands to thethird machine using the first channel in the first frequency band. 8.The system of claim 1, wherein the transmit antenna is a directionalantenna arranged to point a main lobe of a radiation pattern along alength of the first machine and point a null of the radiation patterntowards a second wirelessly controlled machine disposed in a sharedspace with the first machine.
 9. The system of claim 1, wherein thefirst machine comprises a plurality of wirelessly controlled robots thatperform the first commands so long as the first heartbeat signal isreceived.
 10. The system of claim 9, wherein the plurality of wirelesslycontrolled robots each receive the first commands using a same channelin the first frequency band.
 11. A method, comprising: wirelesslytransmitting first commands to a first wirelessly controlled machineusing a first frequency band, wherein the first wirelessly controlledmachine comprises at least one receive antenna; and wirelesslytransmitting a first heartbeat signal to the first machine using asecond frequency band, wherein the first machine performs the firstcommands so long as the first heartbeat signal is received.
 12. Themethod of claim 11, further comprising: transmitting the first commandsduring a first timeslot and not transmitting the first commands during asecond timeslot; and transmitting the first heartbeat signal during boththe first and second timeslots.
 13. The method of claim 11, furthercomprising: wirelessly transmitting second commands to a receive antennaof a second wirelessly controller machine using a first channel in thefirst frequency band, wherein the first commands are transmitted to thefirst machine using a second channel in the first frequency band, andwherein at least one of the first commands and the first heartbeatsignal reach the receive antenna in the second machine.
 14. The methodof claim 13, further comprising: wirelessly transmitting a secondheartbeat signal to the receive antenna of the second wirelesslycontroller machine using a first channel in the second frequency band,wherein the first heartbeat signal is transmitted to the first machineusing a second channel in the second frequency band.
 15. The method ofclaim 11, wherein transmitting the first commands to the first machinecomprises: transmitting the first commands to the first machine using aplurality of transmit antennas and MIMO.
 16. The method of claim 11,wherein transmitting the first commands to the first machine comprises:transmitting the first commands using a plurality of repeaters disposedat different locations along a length of the first machine, wherein theplurality of repeaters use a same channel in the first frequency band totransmit the first commands.
 17. The method of claim 11, furthercomprising: wirelessly transmitting the first commands to the firstmachine using a first channel in the first frequency band; wirelesslytransmitting second commands to a second wirelessly controlled machineusing a second channel in the first frequency band; and wirelesslytransmitting third commands to a third wirelessly controlled machineusing the first channel in the first frequency band, wherein the thirdmachine is spaced a greater distance from the first machine than thesecond machine in a shared space.
 18. The method of claim 11, wherein atransmit antenna used to transmit the first commands is a directionalantenna arranged to point a main lobe of a radiation pattern along alength of the first machine and point a null of the radiation patterntowards a second wirelessly controlled machine disposed in a sharedspace with the first machine.
 19. The method of claim 11, wherein thefirst wirelessly controlled machine comprises a plurality of wirelesslycontrolled robots that perform the first commands so long as the firstheartbeat signal is received.
 20. The method of claim 19, wherein theplurality of wirelessly controlled robots each receive the firstcommands using a same channel in the first frequency band.